字符串函数库-搜索类型_PHP

兼容：(PHP 3, PHP 4, PHP 5)
strpos -- Find position of first occurrence of a string
查找字符在字符串第一次出现的位置
语法：int strpos ( string haystack, mixed needle [, int offset] )
返回值：整数
函数种类: 资料处理

内容说明：
英文：
Returns the numeric position of the first occurrence of needle in the haystack string. Unlike the strrpos(), this function can take a full string as the needle parameter and the entire string will be used.
If needle is not found, strpos() will return boolean FALSE.

If needle is not a string, it is converted to an integer and applied as the ordinal value of a character.
The optional offset parameter allows you to specify which character in haystack to start searching. The position returned is still relative to the beginning of haystack.

中文：
传回参数 needle在字串 haystack中第一次出现的位置，以数字表示。不像strrpos( )，此函式可以取参数 needle全部的字串，而且会使用全部的字串。如果找不到参数 needle，则传回 false。

如果参数 needle不是字串时，它会转换成整数并且按照字元的顺序值来使用。
参数 offset允许你去指定在 haystack中从那一个字元开始搜寻，传回的位置依然是相对於 haystack的起点。

*值得注意的是 needle 只能是一个字符，中文字等就不适合了。

例子讲解：
php

$mystring = 'abc';

$findme= 'a';

$pos = strpos($mystring, $findme);



// Note our use of ===.Simply == would not work as expected

// because the position of 'a' was the 0th (first) character.

if ($pos === false) {

echo "The string '$findme' was not found in the string '$mystring'\";

} else {

echo \"The string '$findme' was found in the string '$mystring'\";

echo \" and exists at position $pos\";

}



// We can search for the character, ignoring anything before the offset

$newstring = 'abcdef abcdef';

$pos = strpos($newstring, 'a', 1); // $pos = 7, not 0

?>
strpos()与substr_count()对比：
php

$mystring = "Hello Chris\";

if (substr_count($mystring, \"Hello\") == 0)

echo \"no\";

// same as:

if (strpos($mystring, \"Hello\") === false)

echo \"no\";

?>

对比下面两个代码注意数字情况下，容易出现的错误，数字整数情况下不能看成字符串。
php

$val1=123;

$val2="123,456,789\";

if (strpos($val2, $val1)!==false) echo \"matched\";

else echo \"not matched\";

?>
结果为： not matched

php

$val1=(string)123;

$val2="123,456,789\";

if (strpos($val2, $val1)!==false) echo \"matched\";

else echo \"not matched\";

?>
结果为：not matched